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Scheme 6.4.3.1. Electrocatalytic cycle of CYP
(Adapted and modified from http://metallo.scripps.edu/promise/CYTOCHROMES.html)
% # #
The direct electrochemistry and electro-catalytic properties of microsomal CYP from A.
terreus MTCC 6324 immobilized on MWCNT-NF/PEI modified GCE were investigated. A pair of well defined and nearly reversible cyclic voltammetric peaks for Fe3+/Fe2+ redox couple of CYP with formal potential (E°) of about -0.53 V (vs. Ag/AgCl reference electrode) in pH 8.0 buffer was observed under deoxygenated condition. In the presence of oxygen and substrate, the redox potential of the bioelectrode was shifted to -0.475 V. Electro-catalytic current with n- hexadecane and inhibition studies with PBO confirmed the involvement of Fe3+/2+ system ofCYP in the redox process. The bioelectrode exhibited a remarkable electro-catalytic activity towards the n-hexadecane substrate. The current response increased linearly from 1 µM to 100 µM of substrate with detection limit 0.1 µM n-hexadecane. The IC50 for PBO was 2.7 µM. The surface coverage of CYP immobilized on MWCNT-NF/PEI modified GCE was approximately 3.45×10-
10 mol cm-2, suggesting enzyme monolayer formation. The electron transfer rate constant (Ks) was 1.0±0.2 s-1, indicating facilitation of the electron transfer between CYP and GCE. A significant positive shift in the redox potential of CYP in the presence of oxygen and substrate is one of the interesting findings, which supports the theory of thermodynamic switch present in CYP catalytic systems. The results have established the potential of the CYP from A. terreus and their fabrication procedure for their application in bioelectronic devices, such as bio-fuel cells.
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Fig. 6.6.1. AFM images of different layers of modifications of GCE for immobilization of CYP.
(A) Bare GCE, (B) GCE/MWCNT-NF, (C) GCE/MWCNT-NF/CYP and (D) GCE/MWCNT- NF/CYP/PEI. Scales in all axes are in nm.
A B
C D
Fig. 6.6.2. The cyclic voltammogram of microsomal CYP immobilized on MWCNT-NF/PEI modified GCE in absence of oxygen. Arrow head points to the background subtracted redox peaks. Background subtraction was carried out by GPES software tool. The voltammogramms were recorded in 50 mM tris buffer (pH 8.0) and scan rate of 100 mV s-1.
Fig. 6.6.3. (A) Cyclic voltammograms of MWCNT-NF/CYP/PEI modified GCE at different scan rates in 50 mM tris buffer (pH 8.0). The scan rates were 10-800 mV s−1. (B) Plot of peak currents vs. scan rates. (C) Variation of peak potentials vs. the logarithm of the scan rates.
A
B C
Fig. 6.6.4. Cyclic voltammograms of GCE/MWCNT-NF/CYP/PEI in absence (a) and presence (b) of oxygen and n-hexadecane. (a’ ) and (b’ ) depicts the background subtracted peaks of (a) and (b), respectively. Voltammograms were recorded in 50 mM tris buffer (pH 8.0) and scan rate of 100 mV s-1.
Fig. 6.6.5. Substrate dependent response of fabricated CYP bioelectrode to different n- hexadecane concentration. (A) Cyclic voltammograms of MWCNT-NF/CYP/PEI modified GCE with successive addition of substrate (ranging from 10-100 µM n-hexadecane). (B) Differential pulse voltammetric (DPV) curves of GCE/MWCNT-NF/CYP-CAT/PEI with different substrate concentration at -0.51 V. (C) Response curve of CYP immobilized on MWCNT-NF/PEI GCE.
(D) Linear calibration curve for determination sensitivity of immobilized CYP.
A B
C D
Fig. 6.6.6. Inhibitor studies with PBO. (A) DPV curves at different PBO concentrations (at fixed substrate concentration of 100 µM and -0.51 V). (B) Linear curve for determination of IC50.
A
B
A membrane bound CYP (Cytochrome P450 monooxygenase) activity was detected in the cells of A. terreus MTCC 6324.
The CYP activity in the n-hexadecane grown cells was largely associated with lipid granules in the cytosol.
The CYP was active with various substrates namely, alkanes, alkane derivatives, alcohols, aromatic compounds, organic solvents, and steroids.
Detection of CYP activity using methanol, acetone, or dimethylsulphoxide as substrate is appealing. Since report on microbial CYP active on these methylated organic solvents as substrate was not available in the open literature.
The CYP was found to catalyze both terminal and sub-terminal oxidations of long-chain hydrocarbon substrates.
Following the heme staining method in SDS–PAGE gel the detected molecular weight of the CYP was ~110 kDa.
The Aspergillus terreus MTCC 6324 had produced very high level of cellular catalase (CAT) during growth on n-hexadecane substrate.
CAT was purified to 160-fold and was found to be a homotetramer with subunit molecular mass of ~90 kDa. The isoelectric pH (pI) of the purified CAT was found to be 4.2.
Peptide mass fingerprinting studies of the CAT protein showed its highest similarity with the CAT B protein. The fully conserved positions for tyrosine (Y) and arginine (R) residues in the proximal heme binding domain of CAT were detected.
CAT was active in a broad range of pH 4.0 to 12.0 and temperature 25ºC to 90ºC. The catalytic efficiency (Kcat/KM) of 4.7×108 M-1 s-1 of CAT was considerably higher than most of the extensively studied catalases from different sources.
The heme from CAT was isolated, purified and identified as heme b.
High stability in a broad alkaline pH range and high temperature stability were identified as interesting characteristics of the isolated CAT.
The stability of CAT was much less in acidic condition than the alkaline environment.
The heme in the CAT protein matrix was disintegrated more in acidic pH and the level of this disintegration increased with decreasing the incubating pH. This heme disintegration has been correlated to the low stability of CAT in acidic pH.
Apo-CAT was prepared by dissociation of heme from the CAT protein matrix at acidic pH and was again reconstituted back with the isolated heme at alkaline and partially denaturing condition to a functionally active enzyme. This preliminary finding on the effective reconstitution of heme to this large catalase protein matrix is expected to pave the way for the potential application of the heme reconstitution approach on the construction of large catalase-based bioelectrode for biosensor or biofuel cell applications.
The high turnover number and excellent stability of CAT was explored for the development of electrochemical-based biosensor. A CAT bioelectrode was fabricated on a GCE using MWCNT, NF and PEI in a layer by layer assembly technique using the adsorption and electrostatic interaction for construction of high electroactive and stable CAT-immobilization matrix. A remarkable electro-catalytic activity of the fabricated bioelectrode towards the reduction of H2O2 was detected. The biosensor response increased linearly with H2O2 concentration from 10 µM to 5 mM. The response time for steady state current and detection limit were ~2 s and 1 µM H2O2, respectively. A high operational and storage stability and stability against leaching were observed for the bioelectrode. A decrease in overall impedance of the bioelectrode upon immobilization of CAT was identified as novel finding.
The direct electrochemistry and bio-electrocatalytic properties of microsomal CYP immobilized on MWCNT-NF/PEI modified GCE were also investigated. A pair of well defined and nearly reversible cyclic voltammetric peaks for Fe(III)/Fe(II) redox couple of CYP with E0 of about -0.53 V was observed. A shift of ~53 mV was observed in the presence of oxygen with E0´ shifting to -0.475. CYP bioelectrode exhibits a remarkable electro-catalytic activity towards the n-hexadecane substrate. The response increased linearly with n-hexadecane concentration from 1 µM to 100 µM with detection limit 0.1 µM. The Ks was 1.0±0.2 s-1, indicating facilitation of the electron transfer between CYP and GCE. Immobilized CYP co-adsorbed with CAT shows linear increase in current with increasing hydrocarbon substrate concentration.
The fabricated CYP bioelectrode showed a high affinity for oxygen and a positive shift in redox potential in presence of oxygen and substrate. This observation on bio-
electrocatalytic property of the fabricated bioelectrode for the hydrocarbon substrates has suggested the potential application of the CYP for the development of biocathode for biofuel cell applications.
The broad substrate specificities of CYP and high catalytic efficiency and broad pH and thermal stability of CAT are the interesting traits of these redox enzymes produced by the filamentous fungi, A. terreus considered in this investigation. Detailed molecular characterization and structural elucidation following conventional molecular biological tools and other techniques like cloning, sequencing, circular dichromism and x-ray crystallography may provide useful structural information of these enzyme proteins which is expected to promote further understanding on the said functional and physical properties of these novel enzymes. The exact location of the redox center (heme in the present case) could also be elucidated with these information that may help the precise wiring of these enzymes either through heme- reconstitution approach or nano-fabrication using suitable ligand chemistry, thus, will advance the scope of promoting better electron-transport kinetics between the redox center of the enzyme and the electronic unit for bioelectronic applications. These are expected to reduce not only the background current and response time but also to increase the current density of the fabricated bioelectrodes. Although, a very low response time and high stability for the CAT biosensor has been achieved, to evaluate the practical application of the fabricated bioelectrode further studies like, analysis of real samples and stability against various parameters such as temperature, pH, salt etc. are essential. The decrease in Rct of the electrode in the presence of immobilized CAT is interesting and has opened up an avenue for detailed structural and electrochemical investigation
of CAT to unfold the observed facts. The other important point need to be considered with respect to CYP is the selection of suitable substrate and media in the cathodic compartment for the proposed fuel cell applications. Highly hydrophobic substrate may cause diffusion limitation;
thus, proper medium engineering for better substrate solubilization and its subsequent sequestration are critical for the increased electron density and overall electrocatalytic efficiency of the CYP-based biocathode for biofuel cell applications.
New insights into P-450 electron transfer. Chem Commun 7:418–419
Agui L, Yanez-Sedeno P, Pingarron JM (2008) Role of carbon nanotubes in electroanalytical chemistry: A review. Anal Chim Acta 622:11–47
Akertek D, Tarhan L (1995) Characteristics of immobilized catalases and their applications in pasteurization of milk. Appl Biochem Biotechnol 50:9555–9560
Akyilmaz E, Kozgus O (2009) Determination of calcium in milk and water samples by using catalase enzyme electrode. Food Chem 115:347–351
Akyilmaz E, Sezginturk MK, Dinc-kaya E (2003) A biosensor based on urate oxidase-peroxidase coupled enzyme system for uric acid determination in urine. Talanta 61:73-79
Allgood GS, Perry JJ (1986) Characterization of a manganese-containing catalase from the obligate thermophile Thermoleophilum album. J Bacteriol 168:563-567
Amo T, Atomi H, Imanaka T (2002) Unique presence of a manganese catalase in a hyperthermophilic archaeon, Pyrobaculum calidifontis VA1. J Bacteriol 184:3305-3312 Andersson LA, Dawson LA (1991) EXAFS spectroscopy of heme containing oxygenases and
peroxidases. Struct Bond 64:1-40
Andersson MM, Hatti-Kaul R (1999) Protein stabilising effect of polyethyleneimine. J Biotechnol 72:21–31
Antonini M, Brunori E (1971) Hemoglobin and myoglobin in their reactions with ligands.
Neuberger A, Tatum EL (eds) North-Holland Publishers, Amsterdam, The Netherlands Armstrong FA, Heering HA, Hirst J (1997) Reactions of complex metalloproteins studied by
protein-film voltammetry. Chem Soc Rev 26:169-179
Armstrong FA, Hill HAO, Walton NJ (1988) Direct electrochemistry of redox proteins. Acc Chem Res 21: 407– 413
Arribas AS, Bermejo E, Chicharro M, Zapardiel A, Luque GL, Ferreyra NF, Rivas GA (2007) Analytical applications of glassy carbon electrodes modified with multi-wall carbon
nanotubes dispersed in polyethylenimine as detectors in flow systems. Anal Chim Acta 596:183–194
Azevedo AM, Miguel D, Prazeres F, Cabral JMS, Fonseca LP (2005) Ethanol biosensors based on alcohol oxidase. Biosens Bioelectron 21 235–247
Barynin VV, Vagin AA, Melik-Adamyan WR, Grebenko AI, Changulov SV, Popov AN, Andrianova ME, Vainshtein BK (1986) Three dimensional structure of the Tcatalase with a 3 Å resolution. Dokl Akad Nauk SSSR 288:877-880
Beers RFJr, Sizer IW (1952) A spectrophotometric method for measuring the breakdown of hydrogen peroxide by catalase. J Biol Chem 195:133-140
Beilen JB, Funhoff EG (2005) Expanding the alkane oxygenase toolbox: new enzymes and applications. Curr Opin Biotechnol 16:308–314
Beyer WF, Fridovich I (1985) Pseudocatalase from Lactobacillus plantarum: Evidence for a homopentameric structure containing two atoms of manganese per subunit. Biochemistry 24:6460-6467
Bistolas N, Christenson A, Ruzgas T, Jung C, Scheller FW, Wollenberger U (2004) Spectroelectrochemistry of cytochrome P450cam. Biochem Biophys Res Commun 314:810–
816
Bistolas N, Wollenberger U, Jung C, Scheller FW (2005) Cytochrome P450 biosensors – a review. Biosens Bioelectron 20:2408–2423
Bradford MM (1976) A rapid and sensitive method for the quantification of microgram quantities of protein utilizing the principle of protein dye binding. Anal Biochem 72:248–
254
Bravo J, Fita I, Ferrer J, Ens W, Hillar A, Switala J, Loewen PC (1997) Identification of a novel bond between a histidine and the essential tyrosine in catalase HPII of Escherichia coli.
Protein Sci 6:1016-1023
Bravo J, Verdaguer N, Tormo J, Betzel C, Switala J, Loewen PC, Fita I (1995) Crystal structure of catalase HPII from Escherichia coli. Structure 3:491-502
Britton LN (1984) Microbial degradation of aliphatic hydrocarbons. In: Microbial degradation of organic compounds (Gibson DT, ed), Marcel Dekker, New York 5:181-252
Brown-Petersen NJ, Salin ML (1993) Purification of a catalase-peroxidase from Halobacterium halobium: Characterization of some unique properties of the halophilic enzyme. J Bacteriol 175:4197-4202
Buleandra M, Radu GL, Tanase I (2000) Redox protein electroanalysis: metalloproteins. Roum Biotechnol Lett 5:423-438
Bullen RA, Arnot TC, Lakeman JB, Walsh FC (2006) Biofuel cells and their development.
Biosens Bioelectron 21:2015-2045
Bushnell LD, Haas FF (1941) The utilization of certain hydrocarbons by microorganisms. J Bacteriol 41:653–673
Buzy A, Bracchi V, Sterijades R, Chroboczek J, Thibault P, Gagnon J, Jouve HM, Hydry- Clergeon G (1995) Complete amino acid sequence of Proteus mirabilis PR catalase.
Occurrence of a methionine sulfone in the close proximity of the active site. J Protein Chem 14:59-72
Calera JA, Sanchez-Weatherby J, Lopez-Medrano R, Leal F (2000) Distinctive properties of the catalase B of Aspergillus nidulans. FEBS Lett 475:117-120
Campanella L, Roversi R, Sammartino MP, Tomassetti M (1998) Hydrogen peroxide determination in pharmaceutical formulations and cosmetics using a new catalase biosensor. J Pharmaceut Biomed 18:105–116
Campanella L, Sammartino MP, Tomassetti M, Zannella S (2001) Hydroperoxide determination by a catalase OPEE: application to the study of extra virgin olive oil rancidification process. Sens Actuators B Chem 76:158-165
Carpena X, Wiseman B, Deemagarn T, Singh R, Switala J, Ivancich A, Fita I, Loewen PC (2005) A molecular switch and electronic circuit modulate catalase activity in catalase- peroxidases. EMBO reports 6:1156-1162
Chance B (1947) An intermediate compound in the catalase-hydrogen peroxide reaction. Acta Chem Scand 1:236-267Chance B (1949) The Reaction of Catalase and Cyanide. J Biol Chem 179:1299-1309
Chandlee JM, Tsaftaris AS, Scandalios JG (1983) Purification and partial characterization of three genetically defined catalases of maize. Plant Sci Lett 29:117-131
Chaplin MF, Bucke C (1990) The large-scale use of enzymes in solution. In: Enzyme Technology, Cambridge University Prees, UK 138-166
Chen H, Mousty C, Chen L, Cosnier S (2008) A new approach for nitrite determination based on a HRP/catalase biosensor. Mater Sci Eng C 28:726–730
Chen X, Xie H, Kong J, Deng J (2001) Characterization for didodecyldimethylammonium bromide liquid crystal film entrapping catalase with enhanced direct electron transfer rate.
Biosens Bioelectron 16:115–120
Claiborne A, Fridovich I (1979) Chemical and enzymatic intermediates in the peroxidation of o- dianisidine by Horseradish peroxidase 1. Spectral properties of the products of dianisidine oxidation. Am Chem Soc 18:2324–2329
Clayton RK (1959) Purified catalase from Rhodopseudomonas spheroides. Biochim Biophys Acta 36:40-47
Cohen G, Rapatz W, Ruis H (1988) Sequence of the Saccharomyces cerevisiae CTA1 gene and amino acid sequence of catalase A derived from it. Eur J Biochem 176:159-163
Coon MJ (2005) Cytochrome P450: Nature’s most versatile biological catalyst. Annu Rev Pharmacol Toxicol 45:1–25
Curatti L, Hernandez JA, Igarashi RY, Soboh B, Zhao D, Rubio LM (2007) In vitro synthesis of the iron molybdenum cofactor of nitrogenase from iron, sulfur, molybdenum, and homocitrate using purified proteins. Proc Natl Acad Sci USA 104:17626- 17631
D’Orazio P (2003) Biosensors in clinical chemistry. Clinica Chimica Acta 334:41–69
Daff SN, Chapman SK, Turner KL, Holt RA, Govindaraj S, Poulos TL, Munro AW (1997) Redox control of the catalytic cycle of flavocytochrome P450 BM3. Biochemistry 36:13816-13823
Das A, Hecht MH (2007) Peroxidase activity of de novo heme proteins immobilized on electrodes. J Inorg Biochem 101:1820–1826
Dashti N, Al-Awadhi H, Khanafer M, Abdelghany S, Radwan S (2008) Potential of hexadecane utilizing soil-microorganisms for growth on hexadecanol, hexadecanal and hexadecanoic acid as sole sources of carbon and energy. Chemosphere 70:475–479
Davis JJ, Djuricic D, Lo KKW, Wallace ENK, Wong LL, Hill HAO (2000) A scanning tunnelling study of immobilised cytochrome P450cam. Faraday Discuss 116:1–8
Dawson JH, Sono M (1987) Cytochrome P-450 and chloroperoxidase: Thiolate-ligated heme enzymes. Spectroscopic determination of their active site structures and mechanistic implications of thiolate ligation. Chem Rev 87:1255-1276
Day BJ (2004) Catalytic antioxidants: a radical approach to new therapeutics. Therapeutic Focus-Reviews 9:557-566
Degtyarenko KN, North ACT, Perkins DN, Findlay JBC (1998) PROMISE: a database of information on prosthetic centers and metal ions in protein active sites. Nucleic Acids Res 26:376–381
Deutsch HF (1951) A highly active horse erythrocyte catalase. Acta Chem Scand 5:815-819 Di J, Zhang M, Yao K, Bi S (2006) Direct voltammetry of catalase immobilized on silica sol–gel
and cysteine modified gold electrode and its application. Biosens Bioelectron 22:247-252 Diaz A, Munoz-Clares RA, Rangel P, Victor-Julian V, Hansberg W (2005). Functional and
structural analysis of catalase oxidized by singlet oxygen. Biochimie 87:205–214
Diaz A, Rangel P, Montes De Oca Y, Lledias F, Hansberg W (2001) Molecular and kinetic study of catalase-1, a durable large catalase of Neurospora crassa. Free Radical Bio Med 31:1323–1333
Diaz A, Valdes VJ, Rudino-Pinera E, Horjales E, Hansberg W (2009) Structure–function relationships in fungal large-subunit catalases. J Mol Biol 386:218–232
Djuricic D, Fleming BD, Hill HAO, Tian Y (2004) Towards exploiting the electrochemistry of cytochrome P450. In: Trends in molecular electrochemistry (Pombeiro AJL, Amatore C, eds), Marcel Dekker, USA and Fontis Media SA, Switzerland 189-208
Dus K, Katagiri M, Yu CA, Erbes DL, Gunsalus IC (1970) Chemical characterization of cytochrome P-450cam. Biochem Biophys Res Commun 40:1423–1430
Eremin AN, Makarenko MV, Drozhdenyuk AP, Moroz IV, Mikhailova RV (2004) Precipitated, coprecipitated, and carbon-mineral sorbents for isolation of extracellular catalase from Penicillium piceum F-648. Appl Biochem Microbiol 40:433-440
Eriksson CE, Olsson PA, Svensson SG (1971) Denatured hemoproteins as catalysts in lipid oxidation. J Am Oil Chem Soc 48:442-447
Eschenfeldt WH, Zhang Y, Samaha H, Stols L, Eirich LD, Wilson CR, Donnelly MI (2003) Transformation of fatty acids catalyzed by cytochrome P450 monooxygenase enzymes of Candida tropicalis. Appl Environ Microbiol 69:5992-5999
Estabrook RW, Cooper DY, Rosenthal S (1963) The light-reversible carbon monoxide inhibition of the steroid C-21 hydroxylation system of the adrenal cortex. Biochem J 338:741–755
Estabrook RW, Faulkner KM, Shet MS, Fisher CW (1996) Application of electrochemistry for P450-catalysed reactions. Meth Enzymol 272: 44-51
Estabrook RW, Werringloer J (1978) The measurement of difference spectra: application to the cytochromes of microsomes. Methods Enzymol 52:212–220
Estavillo C, Lu Z, Jansson I, Schenkman JB, Rusling JF (2003) Epoxidation of styrene by human cyt P450 1A2 by thin film electrolysis and peroxide activation compared to solution reactions. Biophys Chem 104:291-296
Fantuzzi A, Fairhead M, Gilardi G (2004) Direct electrochemistry of immobilized human cytochrome P450 2E1. J Am Chem Soc 126:5040-5041
Fleisher B (1974) Isolation and characterization of golgi apparatus and membranes from rat liver.
Methods Enzymol 31:180–191
Fleming BD, Johnson DL, Bond AM, Martin LL (2006) Recent progress in cytochrome P450 enzyme electrochemistry. Expert Opin Drug Metab Toxicol 2:581-589
Fleming BD, Tian Y, Bell SG, Wong LL, Urlacher V, Hill HA (2003) Redox properties of cytochrome P450BM3 measured by direct methods. Eur J Biochem 270:4082-4088
Folsch J, Less M, Stanley S (1957) A simple method for the isolation and purification of total lipids from animal tissues. J Biol Chem 226:497–509
Fowler T, Rey MW, Vaha-Vahe P, Power SD, Berka RM (1993) The catR gene encoding a catalase from Aspergillus niger: primary structure and elevated expression through increased gene copy number and use of a strong promoter. Mol Microbiol 9:989–998 Fraaije MW, Roubroeks HP, Hagen WR, Van-Berkel WJ (1996) Purification and
characterization of an intracellular catalase-peroxidase from Penicillium simplicissimum.
Eur J Biochem 235:192-198
Fruk L, Kuo C-H, Torres E, Niemeyer CM (2009) Apoenzyme reconstitution as a chemical tool for structural enzymology and biotechnology. Angew Chem Int Ed 48:1550–1574
Fu C, Maier RJ (1992) Nickel-dependent reconstitution of hydrogenase apoprotein in Bradyrhizobium japonicum Hupc mutants and direct evidence for a nickel metabolism locus involved in nickel incorporation into the enzyme. Arch Microbiol 157:493- 498 Galston AW, Bonnichsen RK, Arnon DI (1952) The preparation of highly purified spinach leaf
catalase. Acta Chem Scand 5:781-790
Garcia P, Bruix M, Rico M, Ciofi-Baffoni S, Banci L, Shastry MCR, Roder H, Woodyear T de Lumley, Johnson CM, Fersht AR, Barker PD (2005) Effects of heme on the structure of the denatured state and folding kinetics of cytochrome b562. J Mol Biol 346:331–344 Garre V, Muller U, Tudzynski P (1998) Cloning, characterization, and targeted disruption of
cpcat1, coding for an in planta secreted catalase of Claviceps purpurea. Mol Plant Microbe Interact 11:772–783
Gebicka L, Gebicki JL (1998) Interaction of sodium bis (2-ethylhexyl) sulfosuccinate (AOT) with catalase and horseradish peroxidase in an aqueous solution and in the reverse micelles of AOT/n-heptane. Biochem Mol Biol Int 45:805-811
Gilardi G, Meharenna YT, Tsotsou GE, Sadeghi SJ, Fairhead M, Giannini S (2002) Molecular Lego: design of molecular assemblies of P450 enzymes for nanobiotechnology. Biosens Bioelectron 17:133–145
Gilles-Gonzalez M-A, Gonzalez G (2005) Heme-based sensors: defining characteristics, recent developments, and regulatory hypotheses. J Inorg Biochem 99:1–22
Goldberg I, Hochman A (1989) Three different types of catalases in Klebsiella pneumoniae.
Arch Biochem Biophys 268:124-128
Gooding JJ (2005) Nanostructuring electrodes with carbon nanotubes: A review on electrochemistry and applications for sensing. Electrochim Acta 50:3049–3060
Goswami P, Cooney JJ (1999) Sub-cellular localization of enzymes involved in oxidation of n- alkane by Cladosporium resinae. Appl Microbiol Biotechnol 51:860–864
Gruft H, Ruck R, Traynor J (1978) Properties of a unique catalase isolated from Aspergillus niger. Can J Biochem 56:916–919
Guan L, Scandalios JG (1995) Developmentally related responses of maize catalase genes to salicylic acid. Proc Natl Acad Sci USA 92:5930-5934
Guengerich FP (1991) Reactions and significance of cytochrome P-450 enzymes. J Biol Chem 266:10019–10022
Hamachi I, Tanaka S, Shinkai S (1993) Light-driven activation of reconstituted myoglobin with a ruthenium tris (2, 2'-bipyridine) pendant. J Am Chem Soc 115:10458-10459
Haraguchi H, Mochida Y, Sakai S, Masuda H, Tamura Y, Mizutani K, Tanaka O, Chou WH (1996) Protection against oxidative damage by dihydroflavonols in Engelhardtia chrysolepis. Biosci Biotechnol Biochem 60:945–948